JP4052218B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus using a motor as a generation source of steering assist force.

  Automobile steering is performed by turning a steering wheel arranged inside the passenger compartment to a steering mechanism arranged outside the passenger compartment for steering the steering wheel (generally the front wheels). Done.

As shown in FIG. 1, an electric power steering device for an automobile includes, for example, a first steering shaft 2 whose upper end is connected to a steering wheel 1 for steering, and a lower end of the steering shaft 2 via a torsion bar 3. A torque applied to the first steering shaft 2 by rotating the steering wheel 1 and the second steering shaft 4 connected to a steering mechanism whose upper end is connected coaxially and whose lower end is connected to a wheel. Torque sensor 5 detected by torsion occurring in bar 3, steering assist motor 6 driven based on the detection result of torque sensor 5, and the output shaft of motor 6 are connected to reduce the rotation of the output shaft. A speed reduction mechanism 7 having a worm 71 and a worm wheel 72 for transmitting to the second steering shaft 4, and assisting the operation of the steering mechanism in accordance with the rotation of the steering wheel 1 by the rotation of the motor 6. luck It is configured so as to reduce the person of the labor burden.
Special table 2002-518242 gazette JP 2002-211141 A JP 2002-67992 A Japanese Patent No. 3376869

  The worm wheel of the speed reduction mechanism is made of synthetic resin so that a large noise is not generated between the worm and the worm wheel. However, dimensional accuracy variation, expansion / contraction due to temperature change, swelling due to moisture absorption, and aging The size changes due to wear due to use. When the worm wheel becomes large, a large force is applied to the meshing portion with the worm (the worm may bend), and there is a problem that the steering feeling and the steering characteristics by the steered wheels are deteriorated. Further, when the worm wheel is small, there is a problem that rattling occurs and abnormal noise is generated.

  Patent Document 1 discloses a worm gear including a spring member provided between a gear box housing and a bearing supporting a free end of a worm gear shaft, or a biasing means including a torsion spring adapted to act on a bearing assembly. A power assist type steering is disclosed in which a shaft that holds the gear is biased to engage with a shaft that holds the gear. However, in this power assist type steering, since a leaf spring is used as a biasing means, a sufficient bias stroke cannot be obtained, and there is a possibility that a change in size due to wear cannot be absorbed. Further, since a tilt is applied to the shaft holding the worm gear with the bearing as a fulcrum, a clearance for absorbing the tilt is necessary around the bearing, and noise may be generated by the clearance and the bearing. .

  In Patent Document 2, the first and second bearings that rotatably support the first and second ends of the worm shaft, respectively, and the second end of the worm shaft through the second bearing have a diameter. And an electric power steering apparatus having a swing support surface on which the first bearing supports the first end of the worm shaft so as to be swingable. .

  The present invention has been made in view of the above-described circumstances, and even if the size of the worm wheel of the speed reduction mechanism is changed, the steering feeling and the steering characteristics by the steered wheels are not deteriorated. An object of the present invention is to provide an electric power steering device that does not generate any abnormal noise.

The electric power steering device according to the first invention is housed in a housing, both ends are supported by one bearing, and one end is connected to a steering assist motor, and meshes with the drive gear, A driven gear connected to the steering mechanism, and a biasing means for biasing the bearing on the other end of the drive gear in the radial direction so as to apply a preload to the meshing portion of the driven gear, and by rotating the motor An electric power steering apparatus for assisting steering is provided with a bearing housing for housing the bearing on the other end side, and the biasing means is adapted to pull the bearing housing from the driven gear side of the housing. Ah is, also has a part and the housing is in contact of the bearing housing, each face part and the housing are in contact of the bearing housing, the one end side of the bearing A spherical shape centering on the center is formed, and the outer peripheral portion of the bearing on one end side and the housing are in contact with each other, and the outer peripheral portion of the bearing on the one end side and each surface in contact with the housing are at the center of the bearing. No spherical shape with the center point, the outer peripheral portion of a part and the one end side of the bearing of the bearing housing, characterized by Nashitea Rukoto order to slide the housing respectively.

In this electric power steering apparatus, the drive gear is housed in the housing, both ends are supported by one bearing each, one end is connected to the steering assist motor, the driven gear is housed in the housing, and the drive gear. To the steering mechanism. The urging means urges the bearing on the other end side of the drive gear in the radial direction so as to apply preload to the meshing portion with the driven gear, and assists steering by rotating the motor. The bearing housing houses the bearing on the other end side of the drive gear, and the biasing means pulls the bearing housing from the driven gear side of the housing. Further, a part of the bearing housing and the housing are in contact with each other, and each surface with which the part of the bearing housing is in contact with the housing has a spherical shape with the center of the bearing on one end side of the drive gear as the center point. The outer peripheral portion of the bearing on one end side of the drive gear and the housing are in contact with each other, and the outer peripheral portion of the bearing on the one end side of the drive gear and the surface in contact with the housing are centered on the center of the bearing on the one end side of the drive gear. It has a spherical shape. A part of the bearing housing and the outer peripheral portion of the bearing on one end side of the drive gear are slid with the housing.

According to a second aspect of the present invention, there is provided an electric power steering apparatus, wherein an elastic member is sandwiched between an outer peripheral portion of the bearing housing and the housing, and each inner end face of each inner ring or each outer ring of each outer bearing. An elastic member is attached to the end face.

  In this electric power steering device, an elastic member is sandwiched between the outer peripheral portion of the bearing housing and the housing, and each inner end surface of each inner ring or each outer end surface of each outer ring of each one bearing at both ends of the drive gear. An elastic member is attached to the.

According to a third aspect of the present invention, there is provided an electric power steering apparatus for loosely fitting a columnar protrusion provided on a part of the bearing housing and the columnar protrusion to prevent the columnar protrusion from moving in the axial direction of the driven gear. Further provided with a long hole that is long in the pulling direction of the urging means, and a portion that comes into contact with the long hole when the movement of the columnar protrusion is suppressed forms a flat surface. It is characterized by that.

  In this electric power steering apparatus, a columnar protrusion is provided in a part of the bearing housing, and a long hole in the pulling direction of the biasing means loosely fits the columnar protrusion, and the columnar protrusion moves in the axial direction of the driven gear. It is provided in the housing in order to suppress this. A portion that comes into contact with the elongated hole when the axial movement of the driven gear of the columnar protrusion is suppressed forms a flat surface.

With the electric power steering device according to the first aspect of the invention, even if the size of the worm wheel of the speed reduction mechanism changes, the steering feeling and steering characteristics of the steered wheels do not deteriorate, and rattling does not occur. It is possible to realize an electric power steering device that does not generate the problem. In addition, when the urging means is pulled from the driven gear side of the housing, a space for accommodating the urging means can be easily made. In addition, the bearing housing and the bearing on one end side of the drive gear easily move in the pulling direction of the biasing means, and even if the size of the worm wheel of the speed reduction mechanism changes, the steering feeling and steering characteristics by the steered wheels deteriorate. In addition, it is possible to realize an electric power steering device in which no rattling occurs and no abnormal noise is generated.

According to the electric power steering device of the second aspect of the invention, even if the size of the worm wheel of the speed reduction mechanism changes, the steering feeling and steering characteristics by the steered wheels do not deteriorate, and rattling does not occur. It is possible to realize an electric power steering device that does not generate the problem. Also, the so-called wall feeling at the start of assist output can be eliminated.

According to the electric power steering device of the third aspect of the invention, even if the size of the worm wheel of the speed reduction mechanism is changed, the steering feeling and steering characteristics by the steered wheels are not deteriorated, and rattling does not occur. It is possible to realize an electric power steering device that does not generate the problem. Further, the drive gear does not shift in the axial direction of the driven gear, and the rotation of the drive gear can be accurately transmitted to the driven gear. Further, wear of the columnar protrusions and the long holes can be reduced.

Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.
Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing the configuration of Embodiment 1 of the electric power steering apparatus according to the present invention. This electric power steering apparatus has one end connected to a steering wheel 1 for steering and a first steering shaft 2 having a cylindrical portion at the other end, and one end of the steering shaft 2 inserted into the cylindrical portion. Are connected to the torsion bar 3 which is twisted by the action of the steering torque applied to the steered wheel 1 and one end is connected to a steering mechanism connected to the wheel, and the other end is connected to the other end of the torsion bar 3 coaxially. The second steering shaft 4 is provided.

  The electric power steering apparatus also includes a torque sensor 5 that detects a steering torque applied to the steered wheels 1 based on a relative rotational displacement amount of the first and second steering shafts 2 and 4 according to the twist of the torsion bar 3, and a torque. A steering assisting motor 6 driven based on the torque detected by the sensor 5, a worm 71 (driving gear) that is linked to the rotation of the motor 6, decelerates the rotation and transmits it to the second steering shaft 4, and A speed reduction mechanism 7 having a worm wheel 72 (driven gear) and a housing 8 in which the torque sensor 5 and the speed reduction mechanism 7 are accommodated are provided. A motor 6 is attached to the housing 8. The housing 8 is connected to the first storage portion 8a for storing the torque sensor 5, the second storage portion 8b for storing the worm wheel 72, and the storage portion 8b. And a third accommodating portion 8c.

  FIG. 2 is a cross-sectional view showing the speed reduction mechanism 7 portion. The accommodating portion 8c is elongated in the axial direction of the worm 71, and a first fitting hole 81 and a holding hole 82 communicating with the fitting hole 81 and the long hole 85 are provided at one end in the longitudinal direction. . In the holding hole 82, the first rolling bearing 9 (bearing on the other end side) that supports the shaft portion 71 a at one end of the worm 71 is arranged in the radial direction so as to preload the meshing portion of the worm 71 with the worm wheel 72. A biasing means 10 for biasing is held. The biasing means 10 is made of an elastic body such as a coil spring, and protrudes from the end face of the bearing housing 30 that accommodates the rolling bearing 9, and pulls the columnar protrusion 30a penetrating the elongated hole 85 toward the worm wheel 72 side. By doing so, the rolling bearing 9 is urged | biased in the direction which applies a preload to the said meshing part.

  A second fitting hole 83 and a screw hole 84 continuous to the fitting hole 83 are provided at the other end of the housing portion 8c, and the screw ring 20 for adjusting the axial position of the worm 71 is screwed into the screw hole 84. A lock nut 21 is screwed onto the screw ring 20. Further, a motor 6 having a case communicating with the third accommodating portion 8c is attached to the housing 8.

  The speed reduction mechanism 7 includes a shaft portion 71 b connected to the output shaft 60 of the motor 6, a worm 71 having the shaft portion 71 a, and a worm wheel 72 fitted and fixed in the middle of the second steering shaft 4. The rotation of the output shaft 60 is decelerated and transmitted to the second steering shaft 4 by the meshing of the worm wheel 72 and the worm wheel 72, and a steering mechanism (for example, a rack and pinion type) is transmitted from the second steering shaft 4 through a universal joint (see FIG. (Not shown).

  The worm 71 is arranged so as to cross the axis of the second steering shaft 4, and the first and second rolling bearings 9 and 22 are fitted to shaft portions 71a and 71b provided integrally at both ends thereof. It is. The first rolling bearing 9 is accommodated in the bearing housing 30, and the end surface of the bearing housing 30 where the columnar protrusion 30 a protrudes and the inner surface of the first fitting hole 81 in contact with the end surface are The second rolling bearing 22 is formed into a spherical shape having a center P as a center point. A low friction sheet 37 is sandwiched between the end surface of the bearing housing 30 formed into a spherical shape and the inner surface of the fitting hole 81 so as to be easily slid.

  As shown in FIG. 3, the columnar protrusion 30 a passes through an elongated hole 85 in a direction in which the biasing means 10 pulls between the cores of the worm 71 and the worm wheel 72, and the axial direction of the worm wheel 72 (tooth trace) In order to stop the change in the direction) by surface contact with the inner surface of the long hole 85, a portion in contact with the inner surface of the long hole 85 is formed on the flat surface 30b. The elongated hole 85 is formed by a base material or an elastic body (grommet built-in) of the housing 8.

  The second rolling bearing 22 is a self-aligning bearing in which the outer peripheral portion and the second fitting hole 83 in contact with the outer peripheral portion are formed in a spherical shape with the center P of the rolling bearing 22 as the center point, The outer peripheral portion of the rolling bearing 22 can slide with the fitting hole 83. On the other hand, the outer diameter of the bearing housing 30 is slightly smaller than the inner diameter of the first fitting hole 81 as shown in FIG. It is installed around. An O-ring 31 (elastic member) is fitted in the groove 32 so that the bearing housing 30 does not collide with the fitting hole 81 to generate abnormal noise.

  As shown in FIG. 4A, when the width of the O-ring 31 protruding from the groove 32 is b and the gap between the O-ring 31 and the fitting hole 81 is a, the preload at the meshing portion of the worm 71 and the worm wheel 72 is The relationship between the center distances of the worm 71 and the worm wheel 72 is as shown in the graph of FIG. Here, the inter-core distance is defined as the inter-core distance -a to a or-(a + b) to (a + b).

  In the graph of FIG. 4B, A ′ to A are preload generation regions only by the urging means 10 (the spring constant is small), and even if the inter-center distance changes, the change in the preload is small. B ′ to A ′ and A to B are regions where a preload is generated by the O-ring 31 + biasing means 10, and the spring constant of the O-ring 31 (rubber or elastomer) is large. The change will be greater. The area outside B ′ and B is an area where the bearing housing 30 is in direct contact with the inner surface of the fitting hole 81 and is not normally used.

  In the electric power steering apparatus configured as described above, when the worm 71 is incorporated, for example, the worm 71 in which the rolling bearing 9 accommodated in the bearing housing 30 and the rolling bearing 22 are fitted is used as the second fitting hole. The bearing housing 30 inserted into the third housing portion 8c from 83 and housing the rolling bearing 9 is placed in the first fitting hole 81, and the second rolling bearing 22 is placed in the second fitting hole 83, respectively. Then, the screw ring 20 is screwed into the screw hole 84.

  The rotational operating force of the screw ring 20 is transmitted to the worm 71 via the outer ring, rolling element and inner ring of the rolling bearing 22, and the axial clearance of the rolling bearing 22 is eliminated, and the worm 71 is moved to the first rolling bearing 9. Move towards Further, the rotational operating force of the screw ring 20 is transmitted from the worm 71 to the bearing housing 30 via the inner ring, the rolling elements and the outer ring of the first rolling bearing 9, and the axial gap of the rolling bearing 9 is eliminated. Prevents backlash in the axial direction.

  Next, by urging the urging means 10 on the columnar protrusion 30a of the bearing housing 30, preload can be applied to the meshing portion of the worm 71 with the worm wheel 72, and the backlash amount of the meshing portion can be reduced. I can do it. Further, the backlash amount can be reduced even when the meshing state changes with time due to wear of the teeth of the worm 71 and the worm wheel 72. In addition, by making the biasing means 10 a coil spring, it is possible to reduce the change in the preload of the meshing portion with respect to the change in the backlash amount of the meshing portion.

  In addition, since the columnar protrusion 30a of the bearing housing 30 is restrained from moving in the axial direction of the worm wheel 72 by the long hole 85, the worm 71 holds an appropriate meshing position with respect to the axial direction of the worm wheel 72. And torque irregularities can be eliminated. By providing the bearing housing 30, it is possible to attach a low friction sheet 37 or metal to the outer bottom surface of the bearing housing 30, and further, it is possible to provide a spherical seat, and it is necessary to consider the gap with respect to the bearing 9. Disappears.

  Further, the end surface of the bearing housing 30 and the inner surface of the first fitting hole 81 in contact with the end surface are formed into a spherical shape with the center P of the rolling bearing 22 as the center point, and the low friction sheet 37 is sandwiched. The second rolling bearing 22 and the second fitting hole 83 in contact with the outer peripheral portion are self-aligning bearings that are formed in a spherical shape with the center P as the center point. The movement of the worm 71 in the radial direction due to the fluctuation can be performed smoothly.

  In the embodiment described above, the rolling bearing 9 is used as a bearing for supporting one end of the worm 71, but a sliding bearing may be used. The speed reduction mechanism 7 according to the embodiment described above is a worm gear provided with a drive gear 71 that is a worm 71 and a driven gear 72 that is a worm wheel, and is also a driven gear that is a hypoid pinion and a driven wheel that is a hypoid wheel. It may be a hypoid gear provided with a gear. Further, the reduction mechanism may be a bevel gear.

Embodiment 2. FIG.
FIG. 5 is a cross-sectional view showing the speed reduction mechanism portion of the second embodiment of the electric power steering apparatus according to the present invention. In the reduction mechanism of the electric power steering apparatus, the inner surface of the inner ring of the first rolling bearing 9 and the end surface of the worm 71 and the inner surface of the inner ring of the second rolling bearing 22 and the end surface of the worm 71 are arranged. In addition, elastic members 33 and 34 such as rubber, elastomer, or disc spring are sandwiched, respectively. In this case, the shaft portions 71a and 71b of the worm 71 are fitted into the first and second rolling bearings 9 and 22 without being press-fitted.

  In the case of steering, when moving from the dead zone where the assist output is 0 to the assist region where the assist output is applied, conventionally, as shown by the broken line in FIG. ). However, as described above, by sandwiching the elastic members 33 and 34, the assist output can be gently applied as shown by the solid line in FIG. The difference in feeling can be eliminated. Other configurations and operations of the electric power steering device are the same as the configurations and operations of the electric power steering device described in the first embodiment, and thus description thereof is omitted.

Embodiment 3 FIG.
FIG. 7 is a cross-sectional view showing a speed reduction mechanism portion of a third embodiment of the electric power steering apparatus according to the present invention. In the speed reduction mechanism of the electric power steering apparatus, the outer side surface of the outer ring of the first rolling bearing 9 and the bottom surface of the bearing housing 30 and the outer side surface of the outer ring of the second rolling bearing 22 and the second fitting hole. The elastic members 35 and 36 such as rubber, elastomer, or disc spring are sandwiched between the screw ring 20 screwed into the screw hole 84 continuing to 83. In this case, the shaft portions 71 a and 71 b of the worm 71 are press-fitted into the first and second rolling bearings 9 and 22.

  As described above, the operation by sandwiching the elastic members 35 and 36 is the same as the operation described in the second embodiment with reference to FIG. Other configurations and operations of the electric power steering device are the same as the configurations and operations of the electric power steering device described in the first embodiment, and thus description thereof is omitted.

It is sectional drawing which shows the structure of embodiment of the electric power steering apparatus which concerns on this invention. It is sectional drawing which shows the deceleration mechanism part of the electric power steering apparatus shown in FIG. It is explanatory drawing of the long hole and columnar protrusion of the deceleration mechanism shown in FIG. (A) is explanatory drawing of the urging means and O-ring of the deceleration mechanism shown in FIG. 2, (b) shows the relationship between the preload of the meshing part of a worm and a worm wheel, and the center distance of a worm and a worm wheel. It is explanatory drawing. It is sectional drawing which shows the deceleration mechanism part of embodiment of the electric power steering apparatus which concerns on this invention. It is explanatory drawing which shows operation | movement of the electric power steering apparatus which concerns on this invention. It is sectional drawing which shows the deceleration mechanism part of embodiment of the electric power steering apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 1st steering shaft 3 Torsion bar 4 2nd steering shaft 6 Motor 7 Deceleration mechanism 8 Housing 8c 3rd accommodating part 9 1st rolling bearing (bearing of the other end side)
10 urging means 20 screw ring 22 second rolling bearing (bearing on one end side)
30 Bearing housing 30a Columnar protrusion 30b Chamfered surface 31 O-ring (elastic member)
33-36 Elastic member 71 Drive gear (worm)
72 Driven gear (worm wheel)
81 First fitting hole 82 Holding hole 83 Second fitting hole 85 Long hole P Center of the second rolling bearing (center of the bearing on one end side)

Claims (3)

A drive gear housed in a housing, supported at both ends by one bearing and having one end connected to a steering assist motor, a driven gear meshing with the drive gear and connected to a steering mechanism, and the driven gear An electric power steering device comprising: an urging means for urging a bearing on the other end side of the drive gear in a radial direction so as to apply a preload to a meshing portion with the gear, and assisting steering by rotation of the motor in the provided with a bearing housing for housing the other end of the bearing, the biasing means, Ri said Nashitea from the driven gear side so as to pull the bearing housing of said housing and a portion of the bearing housing And the housing is in contact with each other, and a part of the bearing housing and each surface with which the housing is in contact have a spherical shape centering on the center of the bearing on the one end side, and the one end side The outer peripheral part of the bearing and the housing are in contact with each other, and the outer peripheral part of the bearing on the one end side and the respective surfaces that are in contact with the housing have a spherical shape centering on the center of the bearing, and are part of the bearing housing and an outer peripheral portion of the one end side of the bearing, the housing and the electric power steering apparatus according to claim Nashitea Rukoto order to slide respectively. An elastic member is sandwiched between an outer peripheral portion of the bearing housing and the housing, and an elastic member is attached to each inner end face of each inner ring or each outer end face of each outer ring of each one bearing. 1 Symbol placement of electric power steering system. A columnar protrusion provided in a part of the bearing housing; and the biasing means provided in the housing for loosely fitting the columnar protrusion and suppressing the movement of the columnar protrusion in the axial direction of the driven gear. 3. The electric power steering apparatus according to claim 1, further comprising a long hole extending in a direction in which the columnar protrusion is extended, and a portion that comes into contact with the long hole when the movement of the columnar protrusion is suppressed forms a flat surface. .

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